May 9, 2013

New Insight Into Climate Change Impacts On Greenland’s Glaciers

Climate change impacts on the surface of the Greenland Ice Sheet have been widely studied. An understanding, however, of the key processes in iceberg production has eluded researchers for a long time. A new study, led by the Universite Libre de Bruxelles, presents a sophisticated computer model that provides fresh insight into the impact of climate change on the production of icebergs by Greenland glaciers. The model also demonstrates the shape of the ground beneath the ice has a strong effect on its movement.

Ice-loss from the Greenland Ice Sheet has been accelerating over the past decade. This raises concerns with scientists about runaway losses and consequent sea-level rise. Research into the four major Greenland fast-flowing glaciers, however, has enabled researchers to demonstrate that while these glaciers may show several bursts of retreat and periods of high iceberg formation in the future, the rapid acceleration of recent years is unlikely to continue unchecked.

The research team says this is a critical step in understanding how Greenland´s glaciers will add to sea-level rise in the future. The findings, published in the journal Nature, indicate how important a more detailed knowledge of such glaciers is.

The team initially investigated the current behavior of the four glaciers, finding the rate at which they lose ice depends critically on the shape of the fjords in which they sit, and the topography of the rock below them. Then, they designed a computer model for fast-flowing outlet glaciers from their investigations. The model, developed within the EU Ice2Sea program, projected a sea-level rise contribution from the glaciers of 0.8 inches to 2 inches by the year 2200. This is lower than estimates based solely on the extrapolation of current trends.

"I am excited by the way we have managed to create a detailed picture of the workings of the glaciers. It turns out that if the fjord a glacier sits in is wide or narrow it really affects the way the glacier reacts. The important role of the terrain below the ice shows we need to get a much clearer picture of the rest of Greenland's glaciers before we have the whole story,” said Dr. Faezeh Nick, of the Universite Libre de Bruxelles.

The four glaciers - Petermann, Kangerdlugssuaq, Helheim and Jakobshavn IsbrÃ¦ — were chosen because together they drain around 20 percent of the Greenland Ice Sheet. The model predicts as a group the glaciers will lose, on average, 30 to 47 Gigatons (Gt) per year over the 21st century. A gigaton is equivalent to 1 cubic kilometer of water. Lake Geneva contains about 90Gt of water, for comparison.

Professor David Vaughan, who works at the British Antarctic Survey in Cambridge and is head of the ice2sea program said, "We know that the breaking off of icebergs from glaciers is influenced by climate, but this is the first time we've been able make projections of how the most important glaciers in Greenland will be affected by future climate change. The ice2sea research led by Dr Nick shows how a truly international program can make it possible for scientists to work together across different institutions to make significant steps forward."